Identificação de genótipos de cafeeiro quanto a resistência à ferrugem alaranjada

Abstract

Several phytosanitary problems affect the culture of coffee, among them the rust, caused by the fungus Hemileia vastatrix is one of the most common to the culture, causing significant losses. The control of the disease occurs through constant applications of fungicides in the crops, but the use of resistant cultivars has been increasingly sought. Thus, the objectives of this work were to evaluate and identify F4 progenies from the UFLA/Epamig coffee breeding program that show resistance to coffee orange rust (Hemileia vastatrix) and to verify the relationship of resistance to the enzymatic activation of β-1,3 -glucanases and chitinases in addition to soluble lignin and total soluble phenolic compounds. For this, 31 coffee genotypes were used, being 26 F¬4 progenies and five controls, including three resistant (Ametista, MGS Paraíso 2 and Catiguá MG 2) and two susceptible (Catuaí Vermelho IAC 99 and Topázio MG 1190). The plants were inoculated with spores of H. vastatrix and five weekly evaluations were carried out following a rating scale after the appearance of the first symptoms, in addition to collecting leaves at 24, 48, 72, 120, 192 and 216 hours after inoculation for evaluation of chitinase and β-1,3-glucanase and leaves collected 240 hours after inoculation for evaluation of total soluble phenolic compounds and soluble lignin. There was a significant difference between the genotypes evaluated for orange rust severity. Among the evaluated F4 progenies, some resistant to Hemileia vastatrix can be verified when compared with the resistant controls. It was not possible to find a relationship between resistance and/or susceptibility to Hemileia vastatrix and the quantification of the levels of total soluble phenolic compounds, soluble lignin, chitinase and β-1,3-glucanase in the evaluated genotypes.